Now investigators are tasked with unraveling the mystery surrounding their deaths and finding their killer or killers. The three women all vanished between April and December 2006.

Their disappearances were treated as missing persons cases, but that began to change in April this year when construction workers at a Washington apartment building called police to say they’d discovered skeletal remains in a crawl space.

Two more sets of remains were discovered buried nearby a few days later, and all three were determined by the Office of the Chief Medical Examiner to be human, the Metropolitan Police Department said in a news release.

In May, the medical examiner ruled that the manner of death was homicide for all three victims.

Police announced Wednesday that the bodies had been identified as King, Jefferson and Butts — each awoman in her 40s from Washington who had been reported missing.

King, who left behind three daughters, was reported missing by her mother on April 13, 2006. Jefferson was reported missing by her mother on August 1, 2006, and leaves behind a son. Butts was last seen on Christmas Day in 2006 and was reported missing by her sister. She leaves behind a son.

All of them lived in “fairly close proximity to where their remains were found,” said MPD Chief Peter Newsham at a news conference Wednesday, later adding that Jefferson actually lived in the 100 block of Wayne Place, where her body was discovered.

According to Newsham, King and Butts died as a result of gunshot wounds, while Jefferson died of blunt force trauma.

Newsham expressed his condolences to the families of the women in the news conference. “Whenever you have a family member that goes missing, I am sure regardless of how much time has passed, you are always hopeful that they will return.”

CNN was unable to reach family members of King, Jefferson and Butts on Thursday.

A niece of King told CNN affiliate WJLA that she believed her aunt was still alive until she heard the news, but that it brought her some closure. “I thought that she just moved out of state and started a new life,” she said.

‘Tremendous amount of work ahead’

Newsham didn’t rule out the possibility that the murders were the work of a serial killer, telling reporters, “We would always consider that to be a potential in this case,” but that’s unknown at this point.

“I mean, there’s a lot of information that would suggest they are [linked],” Newsham told reporters. “We have three women similar in age, all went missing in the same year and all located in the same geographic vicinity. But other than that we don’t have anything to tie them together.”

King and Jefferson are believed to have been killed by the same suspect or in the same circumstance, Newsham said, because their bodies were discovered buried together and “there was not enough dirt between the two bodies that would indicate that they were put in there at separate times,” Newsham said.

To identify the women, detectives used a profile from the Office of the Medical Examiner to narrow down their search to eight missing women, officials said. The FBI then compared DNA samples from the remains to DNA from family members of the women, and three matched.

While identifying the bodies will help the investigation, Newsham warned that it’s in its early stages.

“There’s still a tremendous amount of work ahead of us to find the person or persons that are responsible for these murders,” he said.

Detectives will begin speaking with their families and people who may have known them to find out if they had any relation to one another — or to the location where their bodies were discovered.

They’re also reviewing old records to find potential witnesses who lived in the area at the time, Newsham said.

Police are asking that anyone who might have information come forward to speak with police, and are offering a $25,000 reward for any information leading to the arrest of an individual connected to the murders, Newsham said.

“If you knew these women, if you frequented the area or lived in the area of the 100 block of Wayne Place, if you were a delivery person or a mail carrier or any of the like and you were in that area during the year of 2006, you may have a bit of information that could be important to us and so please give us a call,” he said. “We’d like to interview you.”